bpf: Add bpf_map iterator

Implement seq_file operations to traverse all bpf_maps.

Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200509175909.2476096-1-yhs@fb.com

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index ffe0b9b..363ab07 100644 (file)
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1082,6 +1082,7 @@ int  generic_map_update_batch(struct bpf_map *map,
 int  generic_map_delete_batch(struct bpf_map *map,
                              const union bpf_attr *attr,
                              union bpf_attr __user *uattr);
+struct bpf_map *bpf_map_get_curr_or_next(u32 *id);
 
 extern int sysctl_unprivileged_bpf_disabled;
 

diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile
index 6a8b0fe..b2b5eef 100644 (file)
--- a/kernel/bpf/Makefile
+++ b/kernel/bpf/Makefile
@@ -2,7 +2,7 @@
 obj-y := core.o
 CFLAGS_core.o += $(call cc-disable-warning, override-init)
 
-obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o bpf_iter.o
+obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o bpf_iter.o map_iter.o
 obj-$(CONFIG_BPF_SYSCALL) += hashtab.o arraymap.o percpu_freelist.o bpf_lru_list.o lpm_trie.o map_in_map.o
 obj-$(CONFIG_BPF_SYSCALL) += local_storage.o queue_stack_maps.o
 obj-$(CONFIG_BPF_SYSCALL) += disasm.o

diff --git a/kernel/bpf/map_iter.c b/kernel/bpf/map_iter.c
new file mode 100644 (file)
index 0000000..8162e0c
--- /dev/null
+++ b/kernel/bpf/map_iter.c
@@ -0,0 +1,97 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright (c) 2020 Facebook */
+#include <linux/bpf.h>
+#include <linux/fs.h>
+#include <linux/filter.h>
+#include <linux/kernel.h>
+
+struct bpf_iter_seq_map_info {
+       u32 mid;
+};
+
+static void *bpf_map_seq_start(struct seq_file *seq, loff_t *pos)
+{
+       struct bpf_iter_seq_map_info *info = seq->private;
+       struct bpf_map *map;
+
+       map = bpf_map_get_curr_or_next(&info->mid);
+       if (!map)
+               return NULL;
+
+       ++*pos;
+       return map;
+}
+
+static void *bpf_map_seq_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+       struct bpf_iter_seq_map_info *info = seq->private;
+       struct bpf_map *map;
+
+       ++*pos;
+       ++info->mid;
+       bpf_map_put((struct bpf_map *)v);
+       map = bpf_map_get_curr_or_next(&info->mid);
+       if (!map)
+               return NULL;
+
+       return map;
+}
+
+struct bpf_iter__bpf_map {
+       __bpf_md_ptr(struct bpf_iter_meta *, meta);
+       __bpf_md_ptr(struct bpf_map *, map);
+};
+
+DEFINE_BPF_ITER_FUNC(bpf_map, struct bpf_iter_meta *meta, struct bpf_map *map)
+
+static int __bpf_map_seq_show(struct seq_file *seq, void *v, bool in_stop)
+{
+       struct bpf_iter__bpf_map ctx;
+       struct bpf_iter_meta meta;
+       struct bpf_prog *prog;
+       int ret = 0;
+
+       ctx.meta = &meta;
+       ctx.map = v;
+       meta.seq = seq;
+       prog = bpf_iter_get_info(&meta, in_stop);
+       if (prog)
+               ret = bpf_iter_run_prog(prog, &ctx);
+
+       return ret;
+}
+
+static int bpf_map_seq_show(struct seq_file *seq, void *v)
+{
+       return __bpf_map_seq_show(seq, v, false);
+}
+
+static void bpf_map_seq_stop(struct seq_file *seq, void *v)
+{
+       if (!v)
+               (void)__bpf_map_seq_show(seq, v, true);
+       else
+               bpf_map_put((struct bpf_map *)v);
+}
+
+static const struct seq_operations bpf_map_seq_ops = {
+       .start  = bpf_map_seq_start,
+       .next   = bpf_map_seq_next,
+       .stop   = bpf_map_seq_stop,
+       .show   = bpf_map_seq_show,
+};
+
+static int __init bpf_map_iter_init(void)
+{
+       struct bpf_iter_reg reg_info = {
+               .target                 = "bpf_map",
+               .seq_ops                = &bpf_map_seq_ops,
+               .init_seq_private       = NULL,
+               .fini_seq_private       = NULL,
+               .seq_priv_size          = sizeof(struct bpf_iter_seq_map_info),
+       };
+
+       return bpf_iter_reg_target(&reg_info);
+}
+
+late_initcall(bpf_map_iter_init);

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index a293e88..de2a755 100644 (file)
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2934,6 +2934,25 @@ static int bpf_obj_get_next_id(const union bpf_attr *attr,
        return err;
 }
 
+struct bpf_map *bpf_map_get_curr_or_next(u32 *id)
+{
+       struct bpf_map *map;
+
+       spin_lock_bh(&map_idr_lock);
+again:
+       map = idr_get_next(&map_idr, id);
+       if (map) {
+               map = __bpf_map_inc_not_zero(map, false);
+               if (IS_ERR(map)) {
+                       (*id)++;
+                       goto again;
+               }
+       }
+       spin_unlock_bh(&map_idr_lock);
+
+       return map;
+}
+
 #define BPF_PROG_GET_FD_BY_ID_LAST_FIELD prog_id
 
 struct bpf_prog *bpf_prog_by_id(u32 id)